1. Field of the Invention
The present invention relates to a cartridge tape drive, and more particularly, to a cartridge tape drive in which a rectangular tape cartridge can be inserted endwise.
2. Description of Related Art
Because of technological innovations relating to small business and personal computers, such computers are becoming increasingly easy to use in an ever expanding number of applications. Improvements in technology have dramatically increased the speed and capacity of these small computers while simultaneously decreasing the cost of producing them. All of these factors, in combination with many others, have fueled a widespread public demand for smaller more powerful computers.
However, the advantages afforded by the increased speed and capacity of small business and personal computers can only be fully realized if there are corresponding improvements in the peripheral equipment associated with such computers. One area of particular concern is that of data storage and backup. The capacity of a typical computer's internal data storage system, typically a hard disk, has increased dramatically. Although there have been improvements in the reliability and capacity of traditional floppy disks, when compared to the internal storage capacity of many small business and personal computers, floppy disks are extremely limited. Accordingly, in order to maintain duplicate or backup copies of the internal memory it is frequently necessary to use a large number of floppy disks. This is both inefficient and inconvenient for the operator.
As a result, there is a demand for a reliable and efficient means of storing large amounts of data which can be quickly and conveniently transferred to or from the internal memory of a computer or some other data storage device. A magnetic tape cartridge such as the standard one-quarter inch tape cartridge defined by the industry standard ANSI X3.55-1977 is well suited as such a storage device. An example of such a tape cartridge is the DC300XL cartridge manufactured by Minnesota Mining and Manufacturing and described in U.S. Pat. No. 3,692,255. The ANSI cartridge measures approximately six inches in length and four inches in width. Further, the cartridge has a pivoting access door along one of its longitudinal edges which must be swung open to allow access to the magnetic tape within the cartridge. With the door fully open, the width of the cartridge is increased to approximately five and three-quarter inches.
This creates a problem because the industry standard for a five and one-quarter inch floppy disk drive requires that the drive fit within a rectangular box measuring three and one-quarter inches in height, five and three-quarter inches in width, and eight inches in length. This standard is referred to hereafter as the form factor or the five and one-quarter inch form factor. Additionally, a half-height form factor having a height of one and five-eighths inches with the same width and length is increasingly popular. As can be appreciated the width of the cartridge with the access door fully opened is approximately the same as the width of the form factors. This makes it extremely difficult to design a tape drive which will allow use of the cartridge and still fit within the form factors established by the industry.
Existing small business and personal computers are designed in accordance with the industry form factors. As a result, the cabinets of such computers cannot readily accommodate drives having dimensions larger than the form factors. Further, consumers are accustomed to the existing form factors and because of their desire for smaller more compact computers are unlikely to accept an increase in the size of drives. As a result, there is a need for a tape drive for the cartridge that is capable of fitting within the five and one-quarter inch form factor or the half height form factor.
Typically, when a drive is mounted within a computer cabinet only the front of the drive is accessible. The front of the drive measures five and three-quarters inches across and either three and one-quarter inches or one and five-eighths inches high, depending on whether the cabinet is designed in accordance with the full height or half height form factor. As a result, it is difficult for the cartridge which is approximately six inches in length to be inserted edgewise through the front of the drive.
Accordingly, one drive which is designed to use the cartridge has a drawer-like design. That is, the drive is designed to slide out of the cabinet like a drawer. This provides access to the side of the drive and allows edgewise insertion of the cartridge into the side of the drive. However, such a system requires a large number of moving parts which are subject to failure. Further, when the drive is slid out from the cabinet, sensitive elements of the drive may be exposed to damage or contamination which may impair the performance of the drive. Additionally, the sliding drive requires specially designed electrical busses or connectors which are likely to wear and possibly fail with extended use.
In an attempt to alleviate the problems associated with the sliding drive, another drive designed for use with the cartridge employs a stationary housing. The cartridge is inserted endwise through the front of the drive. In this drive, a slidable tray extends partially out of the front of the drive. The cartridge is placed on the tray and manually pushed into the drive. As the cartridge and tray are being pushed into the drive a telescoping, pivoting, spring loaded arm partially opens the cartridge access door to expose the tape. The magnetic head of the tape drive is mounted on a pivoting frame within the drive. When the tray and cartridge are in place within the drive, a lever situated on the front of the drive is rotated to pivot the frame, bringing the magnetic head into contact with the tape.
This drive contains a large number of moving parts which are subject to wear and prone to fail. Further, as with the drawer-like drive, the electrical connections to the head and other elements mounted on the pivoting frame typically are designed to allow for movement as the frame is pivoted. As a result, they are subject to wear and failure.
Additionally, it is difficult to ensure precise and reliable positioning of the head with respect to the cartridge. This is because the cartridge is located on a sliding tray and the head is mounted to a pivoting frame. Because both elements are movable there is likely some play between the head and the tape. This problem is exacerbated as the elements of the drive wear during normal use. As a result of the difficulty in maintaining a consistent and precise relationship between the tape and the head, there is an increased likelihood of errors occurring as data is transferred to or from the tape. As the track density of tapes is increased, tolerances are decreased and it is increasingly important to ensure the proper and consistent location of the tape with respect to the head.